For aerodynamic testing of model airplanes and the like in low-temperature environments, use is made of cryogenic wind tunnels into which the test model is placed for subjecting it to a cold gas flow therein. After rigging such a wind-tunnel model in a normal ambient temperature and preparing it for testing in the wind tunnel, the model has to be cooled down to the test temperature prior to insertion into the wind tunnel. Performing such a cooling process in the wind tunnel would cause a considerable energy demand for generating the required cool air.
From "Aeronautical Journal", November 1984, pp. 379 to 394, it is known to place a cold model, after rigging it for testing in the wind tunnel, into a cooling chamber and to cool it down to the wind tunnel temperature. If the model, after undergoing testing in the wind tunnel, has to be changed for a further test run, the model is transferred into a quick change room wherein it is warmed up so that a person can perform work on it. This quick change room is a treatment chamber containing an atmosphere which is breathable for humans. After completion of the work on the model, the model is transported into the cooling chamber and is cooled down again to wind tunnel conditions. This system requires a separate cooling chamber in addition to the treatment chamber. The energy consumption for warming and cooling the model is considerable.
A wind tunnel system known from "Cryogenics", Vol. 28, January 1988, pp. 10 to 21 is provided with a model conditioning room located under the test section of the wind tunnel. After a test run, the operators move the model and its support from the test section into the conditioning room. A horizontal sliding door separates the conditioning room from the wind tunnel. When changes have to be made on the model, the model is warmed to ambient temperature by hot nitrogen. Dry air is introduced into the room prior to entry of the operators. Also this known system requires a large amount of energy for the warming and subsequent cooling of the model.
From AGARD Report No. 774 "Special Course on Advances in Cryogenic Wind Tunnel Technology", pp. 3-1 to 3-12, it is known to extend a channel from the side into the test section of the wind tunnel. This channel allows access to the model in the test section and is designed for human entry. This prior art requires that the model and the complete test section of the wind tunnel are warmed to ambient temperature before work can be carried out on the model.